PowerBook G4, dead screen and beeps

I've a PowerBook G4, it should be the "PowerBook G4 (Gigabit Ethernet)" [named here](http://support.apple.com/kb/HT3065) . It was on the table where I work to gather dust. The screen is dead, but I clearly hear the boot up sound followed by a noise and 3 beeps. I've tried to connect the computer though the DVI port without success, the screen doesn't show anything. Is there any hope to get it working?